Waste heat recovery system of heat source, with Rankine cycle

Abstract

A waste heat recovery system of an engine has a cooling water circuit and a Rankine cycle. Cooling water is circulated between the engine and a radiator in the cooling water circuit. The Rankine cycle has a heater and an expansion device. The heater performs heat exchange between the cooling water heated by the engine and an operation fluid so as to heat the operation fluid in the Rankine cycle. The expansion device expands the heated operation fluid, so as to generate driving power. The heater is arranged in a bypass circuit so as to be in parallel with the radiator with respect to the cooling water flow. Thus, waste heat of the cooling water heated by the engine can be effectively recovered without reducing a cooling capacity of the radiator.

What is claimed is:  
     
         1 . A waste heat recovery system of a heat source that is cooled by a circulation of a thermal medium, the system comprising: 
 a cooling heat exchanger for cooling the thermal medium, disposed in a thermal medium circulating circuit through which the thermal medium is circulated between the cooling heat exchanger and the heat source; and    a Rankine cycle including 
 a heater that performs heat exchange between an operation fluid and the thermal medium heated by the heat source so as to heat the operation fluid, and  
 an expansion device that expands the operation fluid, which is heated by the heater to be evaporated, so as to generate a driving power,  
   wherein the heater is arranged in parallel with the cooling heat exchanger in such a manner that the thermal medium flowing through the heater bypasses the cooling heat exchanger.    
     
     
         2 . The waste heat recovery system of the heat source according to  claim 1 , further comprising a bypass circuit that is branched from a section of the thermal medium circulating circuit where thermal medium is circulated between the heat source and the cooling heat exchanger to bypass the cooling heat exchanger, and merged with a downstream side of the cooling heat exchanger in the thermal medium circulating circuit, wherein the heater is arranged in the bypass circuit.  
     
     
         3 . The waste heat recovery system of the heat source according to  claim 1 , further comprising a heater circuit that includes a heating heat exchanger which performs heat exchange between blown air and thermal medium heated by the heat source so as to heat the blown air, wherein the heater is arranged in the heater circuit.  
     
     
         4 . The waste heat recovery system of the heat source according to  claim 1 , further comprising: 
 a pumping unit disposed in the thermal medium circulating circuit to circulate the thermal medium; and    a switching unit disposed in the thermal medium circulating circuit to adjust a flow distribution between a flow amount of thermal medium to be introduced into the heater and a flow amount of thermal medium passing through the cooling heat exchanger,    wherein at least one of a discharge capacity of the pumping unit and the flow distribution distributed by the switching unit is variable.    
     
     
         5 . The waste heat recovery system of the heat source according to  claim 4 , further comprising a control unit for controlling at least one of the pumping unit and the switching unit.  
     
     
         6 . The waste heat recovery system of the heat source according to  claim 5 , wherein the control unit controls at least one of the pumping unit and the switching unit based on temperature of thermal medium discharged from the heat source in the thermal medium circulating circuit.  
     
     
         7 . The waste heat recovery system of the heat source according to  claim 6 , wherein: 
 the control unit calculates a difference between a target thermal medium temperature and an actual temperature of the thermal medium discharged from the heat source;    when the difference is less than a first threshold, the control unit determines that a temperature of the heat source is excessively low, and controls the switching unit so as to decrease a distribution amount of thermal medium flowing into the cooling heat exchanger when the distribution amount is not substantially zero; and    when the difference is greater than a second threshold, that is higher than the first threshold, the control unit determines that the temperature of the heat source is excessively high, and controls the pumping unit so as to increase the discharge capacity when the pumping unit has an extra discharge capacity.    
     
     
         8 . The waste heat recovery system of the heat source according to  claim 6 , wherein: 
 the control unit calculates a difference between a target thermal medium temperature and an actual temperature of thermal medium discharged from the heat source;    when the difference is less than a first threshold, the control unit determines that a temperature of the heat source is excessively low, and controls the pumping unit so as to decrease the discharge capacity of the pumping unit; and    when the difference is greater than a second threshold that is larger than the first threshold, the control unit determines that the temperature of the heat source is excessively high, and controls the pumping unit so as to increase the discharge capacity.    
     
     
         9 . The waste heat recovery system of the heat source according to  claim 6 , wherein: 
 the control unit calculates a difference between a target thermal medium temperature and an actual temperature of the thermal medium discharged from the heat source;    when the difference is less than a first threshold, the control unit determines that a temperature of the heat source is excessively low, and controls the switching unit so as to decrease a distribution amount of thermal medium distributed by the switching unit to the cooling heat exchanger; and    when the difference is greater than a second threshold, that is higher than the first threshold, the control unit determines temperature of the heat source is excessively high, and controls the switching unit so as to increase the distribution amount.    
     
     
         10 . The waste heat recovery system of the heat source according to  claim 3 , wherein: 
 the heater circuit further includes a second pumping unit for circulating the thermal medium; and    the second pumping unit has a variable discharge capacity.    
     
     
         11 . The waste heat recovery system of the heat source according to  claim 10 , wherein: 
 the heat source is a rotating device; and    the second pumping unit is controlled based on a rotation speed of the rotating device.    
     
     
         12 . The waste heat recovery system of the heat source according to  claim 1 , further comprising a second switching unit for opening and closing a flow passage of thermal medium flowing into the heater, wherein the second switching unit is located on one of an inlet side of the heater and an outlet side of the heater.  
     
     
         13 . The waste heat recovery system of the heat source according to  claim 12 , wherein the second switching unit is provided to change a flow amount flowing into the heater.  
     
     
         14 . The waste heat recovery system of the heat source according to  claim 13 , further comprising a forcibly closing control means that forcibly controls the second switching unit when a temperature of the thermal medium is equal to or greater than a predetermined temperature.  
     
     
         15 . The waste heat recovery system of the heat source according to  claim 1 , further comprising: 
 a driving device that is disposed to obtain a driving power generated in the heat source; and    a refrigerant cycle that includes a compressor driven by the driving device for compressing and circulating refrigerant, wherein:    the expansion device is mechanically coupled with the compressor; and    the expansion device is disposed to add the driving power generated in the expansion device to the compressor, when the driving power is generated in the expansion device.